In Shelley's "The Triumph of Life," lines 248 to 291, there are only a few "similes."
You may recall that a simile, defined by Dr. L. Kip Wheeler, is:
...an analogy or comparison implied by using an adverb such as like or as.
The comparison must take place between two dissimilar things being compared, like a man and a bear, or a woman to sunshine.
The first simile is:
The tutor and his pupil, whom Dominion
Followed as tame as vulture in a chain.
In this case, the tutor and pupil refer to Aristotle and Alexander the Great (the pupil). Dominion is personified here—meaning rule or control, or, similar, domination. There is no control between the two men; neither is stronger than the other—dominion is tamed as if it were chained.
The next simile is:
If Bacon’s spirit [eagle] had not leapt
Like lightning out of darkness
This refers to Francis Bacon's move to change the way of thinking that had originally been introduced by Aristotle, enlightening the world.
And Gregory and John and men divine
Who rose like shadows between Man and god...
...refers to the separation that rose like a "shadow" between Man and god, blamed on Pope Gregory the Great by Shelley, describing a separation caused by organized religion, or the Church.